This invention relates to shaft assemblies capable of length variation and more particularly to a torque transmitting shaft particularly useful for a motor vehicle steering column and having minimal rotational backlash while permitting minimal sliding resistance to the telescoping tube and shaft of the steering column. In a shaft assembly capable of length variation, particularly useful as a torque transmitting shaft for a motor vehicle steering column it is necessary that the steering wheel be adjusted in an axial direction towards or away from the instrument panel of the vehicle. The assembly should have a low friction adjustment with high torque capability and no perceptible backlash. A shaft assembly having these desirable features is disclosed herein.
In accordance with one aspect of the invention there is provided a shaft assembly capable of length variation, particularly useful as a torque transmitting shaft or motor vehicle steering column. The assembly includes a torque transmitting shaft and a tubular portion mounted on the shaft, the shaft and tubular portion being relatively slidable and the tubular portion having internal longitudinal track structure for receiving roller bearing means. The assembly further includes a coupling between the shaft and the tubular portion including first and second roller bearing means on the shaft, at least one of the roller bearing means being affixed to the shaft. The coupling also includes torsion means on the shaft intermediate the roller bearing means so that when the shaft and roller bearing means are assembled with the axially telescoping tube portion, the torsion means imparts a radial twist relative to one of the first and second bearing means to provide preloaded torque resistance to inhibit transmission or rotational backlash through the shaft while the bearing means permits minimal sliding resistance to the telescoping tube and shaft of the shaft assembly. In accordance with one aspect of the invention one of the roller bearing means is freely rotatable on the shaft and the torsion means is a torsion spring fixed at the ends thereof to the first and second roller bearing means so that when the shaft is assembled with the axially telescoping tube the torsion spring imparts a radial twist relative to the freely rotatable bearing means to provide preloaded torque resistance to inhibit transmission or rotational backlash to the shaft while the bearing means permit minimal sliding resistance to the telescoping tube and shaft of the shaft assembly. In accordance with another aspect of the invention both of the roller bearing means are affixed to the shaft at spaced axial and rotational locations and the shaft between the locations includes a torsion bar which creates preload by rotational axial deflection while the bearing means permit minimal sliding resistance to the telescoping tube and shaft of the shaft assembly.
For further objects and advantages of the invention reference may be had to the following drawings in conjunction with the accompanying description.